The invention relates to a traveling-wave valve arrangement with a traveling-wave valve and a linearizing circuit arrangement.
Traveling-wave valves are preferably employed as high-capacity amplifiers in the microwave range, and in particular in satellites. The power lost in the course of operation of such amplifier valves is dissipated as heat into the environment. When such valves are employed with satellites, the heat is dissipated into space through emission, whereby the housing of the valve is typically secured on the inner side of a heat-conducting wall section of the satellite, and the heat lost is dissipated via the housing of the valve into the wall section and emitted by the wall section. The emitting surface may become smaller as the temperature of the surface increases with no change in the emission power. A permissible minimum temperature of the housing of, for example, 100xc2x0 C. is therefore frequently required for the valves. The high component of power lost by the valve collector is partially emitted via separate radiators projecting from the satellite housing.
Traveling-wave valves exhibit a distinct phase response within the operating frequency band. For the purpose of compensating such a phase response, it is known to transmit the control signals for the valves via a linearizing circuit arrangement with a complementary phase response. The circuit arrangement is herein briefly referred to as a linearizer. The connection between the signal generator, the linearizer and the signal input of the valve is typically realized via flexible coaxial connections. This protects the circuit arrangement against damage by the high temperatures of the valve in that it is located with a spacing from the valve.
The present invention is based on the problem of proposing an advantageous traveling-wave valve arrangement with a traveling-wave valve and a linearizing circuit arrangement.
The invention results in a traveling-wave valve arrangement that is available to the user as a linearized traveling-wave valve without the previously required outside wiring while retaining high permissible temperatures of the housing at the same time. The constructional combination reduces the space requirements of the arrangement and avoids the expenditure for connections that is associated with circuit arrangements which otherwise have to be integrated in the feed line. Furthermore, the constructional combination of the linearizer with the traveling-wave valve offers the user substantially simplified handling, and offers the manufacturer the possibility of being able to offer through individual adaptation of the linearizing circuit arrangement to the individual valve a type of valve with guaranteed very good linearity. Influences deteriorating the linearity properties as a result of unfavorable installation measures at the user""s facility can be excluded to a large extent.
An important feature of the arrangement as defined by the invention is the use of an active cooling element that keeps the linearizing circuit arrangement, herein also briefly referred to as the linearizer, at a temperature lower than that of the wall of the valve. The active cooling element is characterized in that it dissipates heat from a colder surface into a warmer surface. Because of the mechanical insensitivity of the simple electrical controls and the long useful life, the active cooling element is preferably a Peltier element.
By employing an active cooling element and due to the power lost in the element, the power loss occurring in the valve arrangement that has to be discharged is in fact increased overall. However, the power loss component caused by the cooling element is low as compared to the power loss of the travelingwave valve, on the one hand, and any minor increase that may occur in the temperature of the housing of the valve due to the additional loss component is not critical, on the other hand.
The temperature of the linearizer is limited by the cooling element to a temperature not critical for the structural components of the linearizer, preferably to 60xc2x0 C. at the most. The cooling element can be employed as an active element with controllable cooling capacity in a temperature control circuit with a temperature sensor for the temperature of the linearizer, whereby the controllability of a Peltier element is again especially advantageous. The linearizing circuit arrangement may be present, for example in the form of a structure on a printed circuit motherboard with a plurality of components, or fully integrated in the form of an individual integrated circuit.
The linearizer is usually arranged in an electromagnetically screened housing in order to avoid interference caused by leakage fields especially of the traveling-wave valve. In the arrangement as defined by the invention, the housing advantageously acts as an additional radiation barrier and heat insulator against the emission of heat from the valve located in the immediate proximity, or from a common housing of the valve arrangement that may enclose also the housing of the linearizer. By designing the inwardly and/or outwardly facing surfaces of the housing for low radiation emission or radiation absorption power for heat radiation, it is possible to further reduce heating of the linearizer via this path of radiation.
The linearizer is mechanically connected with the wall of the valve or with the wall of a common housing of the valve arrangement substantially only via the cooling element, so that no or minimal solid-body heat transfer takes place from the wall to the linearizer. In an advantageous embodiment of the invention, the housing of the linearizer is secured with a surface of the housing on the cooling surface of the cooling element, which therefore serves as the mechanical carrier that is preferably secured with its heat-radiating surface on the valve wall or on a common wall. Also, the heat-emitting surface of the cooling element can be directly joined with a heat-dissipating surface of an object such as an outside wall of a satellite.
In another advantageous embodiment of the invention, the cooling element is arranged, with at least its cooling surface, within the housing of the linearizer, and the cooling element is preferably used directly as the carrier for the linearizing circuit arrangement, in that the linearizer is mechanically secured on the cooling element, as opposed to an arrangement having a common carrier plate. This establishes good thermal contact with the linearizing circuit arrangement. The heat-emitting surface of the cooling element can then be advantageously coupled with a surface of the housing of the linearizer, and the surface can be thermally coupled with a wall of the valve or with a common wall or with a heat-dissipating surface of the object.
The linearizer is advantageously arranged near the radiation generating system and/or the signal input of the valve and far away from the collector of the valve, so that stronger radiation of heat into the linearizer due to the high temperature of the collector, as well as long signal paths from the linearizer to the signal input are avoided.